Fate of the neonicotinoid insecticide cycloxaprid in different soils under oxic conditions

Evaluating the Safety Profile of Cycloxaprid for Seed Treatment: Insights from Plant Uptake, Translocation, and Metabolism

The use of neonicotinoids in agricultural seed treatments faces increased scrutiny due to their adverse effects such as induced pollinator decline. Cycloxaprid is a promising alternative to traditional neonicotinoids with higher efficiency and improved safety profiles. This study systematically investigated the uptake, translocation, and metabolism of cycloxaprid in rice, maize, and water spinach after seed treatment, using 14C isotope tracing and high-resolution mass spectrometry. Results indicated that less than 11% of cycloxaprid was absorbed by the seedlings, with over 85% released into soils. Cycloxaprid predominantly accumulated in the roots and lower leaves, with minimal translocation to upper leaves or edible parts. Subcellular analysis revealed that cycloxaprid and its metabolites predominantly bonded with internal plant matrix molecules, limiting their transport within the plants. Additionally, seven metabolites of cycloxaprid were identified, and a preliminary metabolic pathway in plants was proposed. Compared to conventional neonicotinoids, cycloxaprid displayed lower potential for plant uptake and vertical translocation, thereby reducing risks to nontarget species like pollinators. These findings provide important theoretical support for the promotion of cycloxaprid as a safe seed treatment agent and offer new perspectives for the sustainable use and risk management of neonicotinoid pesticides.

Pyraclostrobin repeated treatment altered the degradation behavior in soil and negatively affected soil bacterial communities and functions

This study investigated the degradation dynamics of the fungicide pyraclostrobin in three apple orchard soils, along with the responses of soil bacterial community compositions, functions, co-occurrence patterns, and soil nitrogen cycling, under repeated treatment strategies in laboratory conditions. The degradation half-lives of pyraclostrobin varied across the soil types, ranging from 15.7 to 43.4 days, in the following order: Anyang soil > Qingdao soil > Yangling soil. Repeated pyraclostrobin treatment affected degradation behaviors across the different soils. Pyraclostrobin significantly inhibited soil microbial activity and reduced soil bacterial diversity, with more pronounced negative effects observed at high-concentration treatment. Pyraclostrobin clearly changed soil bacterial community structures, significantly enriching potentially degradative bacterial genera such as Methylibium and Nocardioides, which showed increases in the relative abundances of 3.0-181.8 % compared with control. Additionally, pyraclostrobin reduced the complexity of soil bacterial networks and modified the diversity of functional modules. Notably, repeated treatment severely disrupted soil nitrogen cycling, with the absolute abundances of amoA, amoB, nifH, nirK, and nirS in high-concentration treatment decreasing by up to 19.4-91.8 % compared with control. Collectively, pyraclostrobin repeated application altered the degradation behavior, inhibited soil microbial activities, modified soil bacterial community structures and co-occurrence patterns, and seriously disrupted soil nitrogen cycling.

Effects of ammonium sulfate on the degradation and metabolism of dinotefuran in soil: Evidence from soil physicochemical properties and bacterial community structure

Ammonium sulfate and dinotefuran are widely used in agricultural practices; however, limited knowledge exists regarding the potential risks associated with their co-exposure. In this study, the impact of ammonium sulfate on the degradation of dinotefuran in four soils was investigated, and the formation of the main metabolites UF, DN, MNG, and NG was also determined. The underlying mechanisms were explored by the impact of ammonium sulfate on soil physicochemical properties as well as soil microorganisms. The half-life of dinotefuran sole exposure in soils were determined between 27.47 and 60.05 days. Co-exposure of ammonium sulfate significantly impeded the degradation of dinotefuran, resulting in 1.70-5.05 times longer half-life, reduced the content of the metabolites and changed their composition. Ammonium sulfate induced significant alterations in the structure and dominance of bacterial communities in the soils. The reduced relative abundance of Bacteroidota, Proteobacteria and Chloroflexi phyla related to dinotefuran degradation. Ammonium sulfate also led to a decrease in soil pH and organic matter content, which were negatively correlated with the degradation. PLS-SEM analysis revealed soil microbial diversity had a significant impact on the degradation of dinotefuran. The findings serve as a cautionary note regarding the risks of co-exposure to fertilizers and pesticides.

Spatiotemporal variations and priority ranking of emerging contaminants in nanwan reservoir: A case study from the agricultural region in huaihe river basin in China

The presence of emerging contaminants (ECs) in drinking water sources is an increasing concern, yet limited data exists on their occurrence and risk in the upper Huaihe River Basin, an important agricultural region in Central China. This study investigated 70 ECs, including pesticide and antibiotics in surface water from drinking water source areas in Nanwan Reservoir along the upper reaches of the Huaihe River Basin to prioritize the ECs based on ecological risk and health risk assessment. A total of 66 ECs were detected in the surface water at least once at the selected 38 sampling sites, with concentrations ranging from 0.04 to 2508 ng/L. Ecological risk assessment using the risk quotient (RQ) method revealed high risks (RQ > 1) from 7 ECs in the dry season and 15 ECs in the wet season, with triazine pesticides as the main contributors. Non-carcinogenic risks were below negligible levels, but carcinogenic risks from neonicotinoid and carbamate pesticides and macrolide antibiotics were concerning for teenagers. Ciprofloxacin exhibited a high level of resistance risk during the wet season. A multi-indicator prioritization approach integrating occurrence, risk, and chemical property data ranked 6 pesticides and 3 antibiotics as priority pollutants. The results highlight EC contamination of drinking water sources in this agriculturally-intensive region and the need for targeted monitoring and management to protect water quality.

Mineralization and residue characteristics of chloramphenicol in aerobic soils: evidence from a carbon-14 study

Chloramphenicol, a broad-spectrum antibiotic employed for controlling bacterial infections, presents an intriguing aspect in terms of its environmental fate in soils. 14C-labeled chloramphenicol was used to explore its mineralization and residue characteristics in three distinct agricultural soils in China. The findings revealed a nuanced pattern in the fate of 14C-chloramphenicol, with notable variations among the different soils under investigation. The chloramphenicol extract residue exhibited a reduction of 18.04% in sandy clay soil, 23.04% in clay loam soil, and 21.73% in loamy clay soil. Notably, the mineralization rate in sandy clay soil was 25.22% surpassed that in the other two soils, particularly during the initial stages of incubation. Over time, the diminishing extract residue underwent conversion into minerals and bound residue. The formation rate of bound residue was increased from 44.59 to 53.65% after adding 10% manure, suggesting that chloramphenicol easily binds with soils rich in organic matter. The bound residue is predominantly localized in the humin fraction across all soils. Additionally, the sterilized soil experiments indicated the pivotal role of microorganisms in influencing the fate of chloramphenicol under the specified experimental conditions. In conclusion, this study offers valuable insights into the environmental dynamics of chloramphenicol in soils, emphasizing the importance of soil composition, organic matter content, and microbial activity. The findings contribute to a scientific understanding of the environmental safety implications associated with chloramphenicol usage.

Development of a simplified human embryonic stem cell-based retinal pre-organoid model for toxicity evaluations of common pollutants

OBJECTIVE

To explore the retinal toxicity of pharmaceuticals and personal care products (PPCPs), flame retardants, bisphenols, phthalates, and polycyclic aromatic hydrocarbons (PAHs) on human retinal progenitor cells (RPCs) and retinal pigment epithelial (RPE) cells, which are the primary cell types at the early stages of retinal development, vital for subsequent functional cell type differentiation, and closely related to retinal diseases.

MATERIALS AND METHODS

After 23 days of differentiation, human embryonic stem cell (hESC)-based retinal pre-organoids, containing RPCs and RPE cells, were exposed to 10, 100, and 1000 nM pesticides (butachlor, terbutryn, imidacloprid, deltamethrin, pendimethalin, and carbaryl), flame retardants (PFOS, TBBPA, DBDPE, and TDCIPP), PPCPs (climbazole and BHT), and other typical pollutants (phenanthrene, DCHP, and BPA) for seven days. Then, mRNA expression changes were monitored and compared.

RESULTS

(1) The selected pollutants did not show strong effects at environmental and human-relevant concentrations, although the effects of flame retardants were more potent than those of other categories of chemicals. Surprisingly, some pollutants with distinct structures showed similar adverse effects. (2) Exposure to pollutants induced different degrees of cell detachment, probably due to alterations in extracellular matrix and/or cell adhesion.

CONCLUSIONS

In this study, we established a retinal pre-organoid model suitable for evaluating multiple pollutants' effects, and pointed out the potential retinal toxicity of flame retardants, among other pollutants. Nevertheless, the potential mechanisms of toxicity and the effects on cell detachment are still unclear and deserve further exploration. Additionally, this model holds promise for screening interventions aimed at mitigating the detrimental effects of these pollutants.

Nonenantioselective environmental behavior of a chiral antiviral pesticide dufulin in aerobic soils

Dufulin is a promising chiral antiviral agent, but little is known about its fate in soils. In this study, the fate of dufulin enantiomers in aerobic soils was investigated using radioisotope tracing techniques. The result of the four-compartment model showed no significant differences in dissipation, generation of bound residues (BR) and mineralization between S-dufulin and R-dufulin during incubation. Dufulin dissipated most quickly in cinnamon soils, followed by fluvo-aquic and black soils and the half-lives of dufulin in these soils obtained by the modified model were 4.92-5.23, 32.39-33.32 and 60.80-61.34 d, respectively. After 120 d incubation, the percentage of radioactivity of BR increased to 18.2-38.4 % in the three soils. Dufulin formed most bound residues in the black soil, least in the cinnamon soil, and BRs rapidly formed in the cinnamon soil during the early culture period. In these three soils, the cumulative mineralization of ¹⁴CO₂ ranged from 25.0 to 26.7 %, 42.1 to 43.4 % and 33.8 to 34.4 %, respectively, which indicated that the environmental fate of dufulin was primarily influenced by soil characteristics. The study of microbial community structure revealed that the phyla Ascomycota, Proteobacteria and genus Mortierella might be related to the degradation of dufulin. These findings provide a reference for assessing the environmental impact and ecological safety of dufulin application.

Wheat straw pyrochar more efficiently decreased enantioselective uptake of dinotefuran by lettuce and dissemination of antibiotic resistance genes than hydrochar in an agricultural soil

Remediation of soils pollution caused by dinotefuran, a chiral pesticide, is indispensable for ensuring human food security. In comparison with pyrochar, the effect of hydrochar on enantioselective fate of dinotefuran, and antibiotic resistance genes (ARGs) profiles in the contaminated soils remain poorly understood. Therefore, wheat straw hydrochar (SHC) and pyrochar (SPC) were prepared at 220 and 500 °C, respectively, to investigate their effects and underlying mechanisms on enantioselective fate of dinotefuran enantiomers and metabolites, and soil ARG abundance in soil-plant ecosystems using a 30-day pot experiment planted with lettuce. SPC showed a greater reduction effect on the accumulation of R- and S-dinotefuran and metabolites in lettuce shoots than SHC. This was mainly resulted from the lowered soil bioavailability of R- and S-dinotefuran due to adsorption/immobilization by chars, together with the char-enhanced pesticide-degrading bacteria resulted from increased soil pH and organic matter content. Both SPC and SHC efficiently reduced ARG levels in soils, owing to lowered abundance of ARG-carrying bacteria and declined horizontal gene transfer induced by decreased dinotefuran bioavailability. The above results provide new insights for optimizing char-based sustainable technologies to mitigate pollution of dinotefuran and spread of ARGs in agroecosystems.

Fate characteristics of the chiral pesticide dufulin in flooded anaerobic soils and its interaction with soil microorganisms

Dufulin (DFL), a plant antiviral agent synthesized in China, has been widely used to control viral diseases in rice, tobacco, tomato, and other crops. However, its fate in flooded anaerobic soils, which is essential for environmental risk assessment, remains unknown. Using the ¹⁴C tracer technique, the fate of ¹⁴C-labeled DFL isomers in flooded anaerobic soils was systematically investigated in this study. Over the 100-day incubation, a small part of ¹⁴C-DFL enantiomer was mineralized to ¹⁴CO₂ (< 10.44 %) or entered the surface water phase (< 6.69 %), with most of the ¹⁴C (> 80.40 %) remaining in the subsoil. The residues in all tested soils were gradually converted from extractable residues (ERs) to nonextractable residues (NERs). At the end of incubation, the fraction of ¹⁴C-NERs reached 5.38-23.77 %. The half-life (t_1/2) of the DFL parent in soil is relatively long under submerged anaerobic conditions, especially in Fluvo-aquic soil, up to 277.26-315.07 days, which exceeds the risk threshold recommended by the Stockholm Convention (< 180 days). Soil type and microbial activity influenced the fate of DFL in flooded soils and microbial analysis showed that 2.0 mg kg^-1 DFL had no obvious impact on soil bacterial richness and function. Pseudomonas spp. was estimated to be a potentially efficient degrading genus for DFL. No enantioselective behaviors were detected in this study. This research provides a theoretical basis for evaluating the environmental impact and ecological safety of DFL application.

Simultaneous determination of the nematicide fluensulfone and its two major metabolites in soils by ultra-high performance liquid chromatography-tandem mass spectrometry

A fast and sensitive method for simultaneously detecting nonfumigant nematicide fluensulfone (FSF) and its two major metabolites [3,4,4-trifluorobut-3-ene-1-sulfonic acid (BSA) and 5‑chloro-1,3-thiazole-2-sulfonic acid (TSA)] in different types of agricultural soils (black soil, krasnozem, sierozem) was established and validated through ultra-high performance liquid chromatography-tandem mass spectrometry. The samples were prepared by a modified quick, easy, cheap, effective, rugged, and safe method. The soil samples were firstly extracted with acetonitrile/water (4/1) and then purified with multi-walled carbon nanotubes (MWCNTs). Parameters influencing purification efficiency and recoveries, such as the type and the amount of sorbent were evaluated and compared. The overall average recoveries of three target analytes in soils were in the range of 73.1%-113.9% and the relative standard deviations (including intra-day and inter-day precision) were less than 12.7%. The limit of quantification was 5 μg/kg for all three compounds. The established method was successfully applied to examine the degradation of FSF and the formation of its two major metabolites in three different types of soil, indicating its efficacy in investigating the environmental behavior of FSF in agricultural soil system.

Environmental fate and metabolism of the systemic triazolinthione fungicide prothioconazole in different aerobic soils

As a best-selling triazolinthione fungicide, prothioconazole (PTZ) has been widely used worldwide and has aroused concern about its environmental effect. This study used phenyl-UL-¹⁴C-labeled PTZ and an improved fate model to investigate the fate and metabolism of this fungicide in aerobic soil. During 120 d of incubation, PTZ rapidly transformed into metabolites and bound residues, with a half-life (DT₅₀) of less than 1 d. After 120 d, approximately 45-55% of PTZ formed bound residues, and the extractable metabolite residues were gradually degraded over time. Approximately 19%, 44% and 27% of phenyl-UL-¹⁴C-PTZ was mineralized in red soil, fluvo-aquic soil and cinnamon soil, respectively, but only approximately 3% was mineralized in black soil. Five metabolites were identified and confirmed, and a possible metabolic pathway for phenyl-UL-¹⁴C-PTZ in soil was proposed. Based on the correlation analysis between soil properties and model rate constants, soil properties exerted important effects on PTZ transformation. These results will provide basic data for environmental risk assessments and removal of the PTZ pollutant and suggest that the soil type should be considered in the selection and application of pesticides.

Computer-aided toxicity prediction and potential risk assessment of two novel neonicotinoids, paichongding and cycloxaprid, to hydrobionts

Paichongding (IPP) and cycloxaprid (CYC) have been effectively used as the alternative products of imidacloprid (IMI) against IMI-resistant insects and exhibit a great market potential. However, risk assessment of IPP and CYC for non-target organisms, especially ecological risk assessment for non-target aquatic organisms, is still lacking. Here, we predicted the toxicity and potential risks of IPP, CYC, and their transformation products (TPs) to hydrobionts. The results indicated that IPP and CYC could generate 428 and 113 TPs, respectively, via aerobic microbial transformation. Nearly half of the IPP TPs and nearly 41 % of the CYC TPs exhibited high or moderate toxicity to Daphnia or fish. Moreover, we found that IPP, CYC, and 80 TPs of them posed potential risks to aquatic ecosystems. Almost all harmful TPs contained a 6-chloropyridine ring structure, suggesting that this structure may be associated with the strong toxicity of these TPs to aquatic organisms, and these TPs (IPP-TP2 or CYC-TP2, IPP-TP197 or CYC-TP71, IPP-TP198 or CYC-TP72, and IPP-TP212 or CYC-TP80) may appear in aquatic environments as final products. The risks posed by these TPs to aquatic ecosystems require more attention. This study provides insights into the toxicity and ecological risks of IPP and CYC.

Superabsorbent hydrogel as a formulation to promote mineralization and accelerate degradation of acetochlor in soils

The excessive use of herbicides had caused serious environmental pollution and ecological problems. Therefore, it is imperative to explore an effective method to reduce herbicide residues and pollution. In the present study, we used superabsorbent hydrogels coated ¹⁴C-acetochlor (SH-ACE) to investigate its behavior in different soils under oxic conditions. After 100 days, the mineralization by SH-ACE was increased by 2.3%, 2.5% and 3.3% in the red clay soils, fluvio-marine yellow loamy soils and coastal saline soils, respectively, compared to the control group. This result indicated that the SH-ACE treatment resulted in more complete degradation and detoxification of acetochlor. In addition, the dissipation rates of acetochlor were significantly faster in the SH-ACE treatment, which reduced the persistence of acetochlor. The probable degradation pathways of acetochlor involved dechlorination, hydroxylation, deethoxymethylation, and the formation of thioacetic acid derivatives in the two treatments, but the contents of transformation products were completely different. These findings suggest that the SH-ACE treatment has a significant effect to accelerate the degradation of acetochlor. When developing green pesticides, we emphasize that superabsorbent hydrogel coating treatment should be considered as a promising method for ecological safety in the environment.